1. Field of the Invention
The present invention relates to the shape of a contact hole provided in a display apparatus, the shape being determined when a transparent conductive oxide (TCO) electrode is connected to wiring (power wiring and/or ground (GND) wiring).
2. Description of the Related Art
A light-emitting device using organic electro luminescence (hereinafter referred to as organic EL) has been provided, for example, for a matrix display apparatus that can perform full-color light emission, the matrix display apparatus including a pixel with a film provided on a substrate, where the film includes materials producing colors including red (R), green (G), and blue (B).
Here, as a method of moving an upper electrode provided on the light-extraction side from a high sheet resistance such as an indium tin oxide (ITO) to GND wiring with a low sheet resistance including aluminum (Al), the method being performed in the light-emitting device, the following technology has been disclosed in US 2005/0200270 (first patent document). According to the above-described document, the opening area of each contact hole is reduced and a plurality of the contact holes is arranged in single file.
However, if the plurality of contact holes is provided in single file along a contact hole display region extending from a TCO electrode to low-resistant wiring, as is the case with US 2005/0200270, parasitic resistances existing between the contact holes are increased. Further, currents intensively flow into the contact holes and the parasitic resistances are increased in appearance, which may cause power losses.
Further, according to U.S. Pat. No. 7,227,312 (second patent document), a plurality of contact holes having the same areas is arranged in three files and the shape of grating in a direction from a display region toward the contact holes.
However, according to the above-described configuration, it is assumed that the amount of currents flowing into the contact holes is decreased as the distance between the display region and the contact holes is increased.
The above-described problem occurs especially when a TCO electrode with a high resistance is electrically connected to wiring with a resistance lower than the resistance of the TCO electrode. This is because when a current flows into the low-resistant wiring via a contact hole provided near the display region, most of the current does not return to the high-resistant TCO electrode.
Therefore, as the distance between the display region and the contact holes is increased, the amount of currents flowing into the contact holes is decreased.
Consequently, the opening area is unnecessarily increased in relation to the amount of currents flowing into the contact holes provided at a distance from the display region so that a narrow frame may be achieved with difficulty.